Originally published on March 17, 2021 7:17 am Humans have changed the Earth in such profound ways that scientists say we have entered a new geological period: the Anthropocene Epoch. But when did the new epoch officially begin? And how, exactly, should it be defined? Those are the questions that geologists are pursuing with increasing urgency at sites around the world. Teams are studying 11 locations on five continents, looking for a place where rock, mud or ice perfectly capture the global impact of humans. As is often the case in science, the teams are both collaborating and competing. They share information, but ultimately only one site will be crowned the "golden spike" location for the Anthropocene: the place on Earth where a line in the rock, mud or ice exemplifies the unique markers of the age of humans.